It’s not removed deliberately. Which type of field is it? – can you show me a screenshot of how it looks in the form and also how it looks in the “field table” in the backend (if it’s listed there).
While troubleshooting this issue we came across another dev instance of the same web site which uses the 4.3.60 and does NOT throw an error, so we will hunt further and find out why the error is being generated. We have proof now that it is NOT DFFS. We will undoubtedly find out it is human error!! LOL